Trans-catheter aortic valve replacement (“TAVR”) has been shown to improve the survival rate in high risk patients for whom surgical heart valve replacement is not an option. However, the long-term clinical success of a TAVR, or any trans-catheter aortic valve implantation (“TAVI”) procedure, is dependent on accurate deployment, anchoring, and acceptable valve performance, both acutely and chronically. This requires maximum reduction, or potential elimination, of the risks associated with paravalvular (PV) aortic regurgitation (AR).
For example, malapposition of the stent frame of a prosthetic valve to the native valve annulus is a major contributing factor for PV AR. In this regard, apposition of the stent may be affected by the degree of calcification of the valve leaflets. Accordingly, highly calcified regions have typically low compliance compared to the non-calcified regions of the native valve annulus. Thus, selecting a proper valve size and assessing the compliance, or lack thereof, of a native valve annulus are important in reducing the risks associated with these procedures. However, determining the proper valve size during a TAVI procedure is difficult due to an inability to easily access the native valve annulus, the presence of calcification and other irregularities, and the eccentricity/elliptical nature of the native valve annulus.
There are a number of ways in which the native valve annulus may be sized in today's clinical practice. They include imaging techniques, such as trans-thoracic echocardiogram (TTE), trans-esophageal echocardiogram (TEE), and angiography. However, these imaging methods are not standardized and may yield different results depending on the view obtained of the native valve annulus with the annulus' elliptical shape contributing to the uncertainty. Although valve sizing using 3D computed tomographic (CT) imaging has been observed to result in less PV AR, this technique is expensive and requires independent patient preparation/assessment prior to the procedure. Additionally, CT imaging exposes the patient to potentially harmful radiation.
Furthermore, alterations to the valve annulus following a balloon valvuloplasty procedure can make it difficult to correctly size the annulus, even with current imaging techniques. Thus, there is a clinical need for an alternative option for accurately sizing a native valve annulus that is cost effective and safe for patients, both before and after a valvuloplasty procedure.